2. Look at the Axle Tag which is attached to the differential cover, under one of the bolts. The numbers on the lower left of the tag should be self-explanantory.

3. Jack the rear of the vehicle up, support it with jackstands, and chock the front tires. Mark the driveshaft and one tire. Put the transmission in neutral. Spin the tire ONE full revolution and count how many times the driveshaft rotates (including partial). The number of driveshaft rotations is the ratio.

4. Jack the rear of the vehicle up, support it with jackstands, and chock the front tires. Remove the differential housing cover. Count the number of teeth on the ring and pinions gears. Divide the ring gear's tooth-count by the pinion gear's tooth-count.